1. Field of Invention
This invention relates to a method of treating dross aluminum oxides and, in particular, to a method for conditioning the oxides for further reaction.
2. Brief Statement of the Prior Art
Waste aluminum oxides, known as dross aluminum oxides, have accumulated about the countryside in substantial quantities. The oxides contain impurities such as potassium and sodium chlorides, up to about 20 weight percent aluminum metal, aluminum nitride and aluminum carbide. Some attempts have been made to utilize these oxides as a cement ingredient, however, the quantities of dross oxides produced in aluminum smelting operations far exceed the quantities needed by the cement industry. Attempts have been made to purify the aluminum oxides of their contaminants and use them in chemical processing as a substitute for aluminum trihydrate or bauxite, however these attempts heretofore have not achieved any significant commercial acceptance. A method for conditioning of the oxides is disclosed in U.S. Pat. No. 3,955,969 in which the oxides are thermally treated with water to decompose the carbide and nitride contaminants. The treated oxides are suggested as useful as a flux for the steel industry.
In U.S. Pat. Nos. 4,252 776 and 4,320,098, it is disclosed that the dross aluminum oxides can be conditioned for use in the chemical industry by thermal treatment with water in the presence of a refractory grinding medium which is effective to react the aluminum metal to aluminum hydroxide and decompose the aluminum carbide and aluminum nitride impurities.
One of the problems encountered in commercializing the aforementioned treatment is that the aluminum oxides severely foam when treated at elevated temperatures in an aqueous suspension. The foaming is often so severe that most of the powdered aluminum oxides are lifted out of the reaction zone, interrupting the treatment of the oxides.